it's actually very complicated to write Amazing Grace in the right rhythm, especially in a 3/4 beat. I think Amazing Grace is more like a Ballad, and if written in 6/8, it sounds a lot better in the right rhythm. I had the same problem but the other way around (wrote it in 6/8 but should be a 3/4) with a Christmas tune, "Little drummer boy", let's see if I can post that here in a few minutes, just as an example.